Reflectoscope



' I C. E. H. ARM BRUSTER 1 REFLECTOSGOPE Filed May 23, 1918 s Sheets-Sheet 1 Z Z0 Z3 33 34 34-35 29 22 INVENTOR C 5. hf Armbrus fer ATTORNEY Oct. 2, 1923.- 1,469,411

C. E. H. ARMBRUSTER REFLECTOS COPE Filed May 23, 1918 5 Sheets-Sheet 5 60 NVENTOR I ATTORNEY Patented Get. 2, 1923.

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CHARLES E. n. i iR viBR srEn, or DEN ER, oorionnno.

i v nnrnncrosoorn To all whom it may concern:

Be it known that I, CHARLES E. H. ARM- .nnusrnn, a citizen of the United States, residing at Denver, 1n the county ofv Denver and Stateof Colorado, have invented certain new and useful lmprovements in Reflectoscopes, of which the. following is a specification. o

, This invention relates to optical instruments of the type used in measuring refractions of the eye and more particularly to 1m:

provement s .in reflectoscopes of the class gshownand described in-my United States I while it is focusing at a near object for the" dyna mic test. l I

St1llother objects of the invention reside ject; i Still another object of the invention is to provide an instrument which may be used in Letters Fatent No. 1190619, issued July 11,:

V7 It is the primary object of thepresent invention to provide a reflectoscope of very tioned which may be used for making static tests of the eye whileit is lookingat infinity,

as well as to measure the dynamic power of the eye while it is focused upon a near obmaking static tests within a limited space and whlch therefore is adapted for: operation in rooms which by reason of their lirn- ,ited dimensions or lack of operating space,

do not afford the distance between theeye of the patient and a test-object, required to produce the. condition of relaxation of the accommodation or focusing power of the eye which is essential in the static test.

Further objects of invention reside in providing an improved appliance for establishmg-a polnt in the visual axis of the eye in the provision'of certain adjustments and novel arrangement of partswhich enhance the accuracy of the instrument and facilitate. its use in measuring refractions of the eye by retinoscopic examination.

An vembodiment of my lnvention in its I preferredi orni has been shown in the accompanying drawings in which like charac- Application filed May 23, 1918. Serial in. 238,181.

' ters of reference designate corresponding parts throughout the various views and in which-V L j i V.

Figure 1 representsa side velevation of the reflectoscope in its operative position with relation to atrial frame of conventional construction 1 Figure 2, a front elevation of the same looking in the direction of the arrow A,

Figure 1,

Figure. 3, a section along the line 3-3,

Figure 1, H

Figure 4,2 section along the line 4-4:,

Figure lfdrawn to an enlarged scale, j-

' .Figure 5, an enlarged section taken on the line 55, Figure 1 with the instrumentin condition for testing the balance oi the muscles of motion of the eye, 1

Figure 6, an enlarged section on the line .66,Figure 1, w Figure 7, a fragmentarysideelevation of the instrument in aicondition for'making the static or distance test, v

Figures 8 9 and 10, diagrammatic representations of the lines of vision and paths 1 of reflected light in statictests made by the 7 use of my improvedrefiectoscope,

Figure 11, a diagrammatic view showing the lines of vision and paths of reflected light inthe dynamic test,

Figure 12, a face view ofa test-chart used in conducting the static tests,

Figure 13, an enlarged'viewof the finding appliance at the back of the mirror of the instrument, and

Figure 14:, a section along the line Figure 13; V I i Referring'to the drawings the reference character 2 designates a trial frame of the construction commonly used in optical in.

struments for the placement of lensesin front of the, eyes ofapatient.

vThe frame 'issupported upon theend of a horizontally extending a'rm 3 of an L- shaped bracket a which is rotatably and vertically adjustably suspended froma" car rier 5. y v i i The carrler 1s movably fitted in a, slide- 'way v6 which is' fastened against; a stationary support such as-a wall of roonifin which the instrument is installed A rod 7 depending from the bracket carries anadjustable'stop 8 which ,byen'gagement with the horizont'a ljarm'of the bracket determines its operative position, and a 1 setscrew 9 onasle'eve lO of the carrier, through which the upright portion of the bracket clamp 13 at one 01 its ends is suspended from the horizontal arm of the trial-frame bracket and which has'atits opposite end a collar it for the rotary support of a horizontally extending bar 15 upon which the operating parts 0t V the instrument are mounted.

A stop 16 on the collar engages the bar to establish its operative position in a vertical plane at rightangles to that passing intermediate of the lens-holders of the trial-frame. The supporting bar is preferably composed of telescoping parts 01' Jangular section which permit of its being lengthened or shortened in the adjustment of the cooperative parts of the-instrument aswill' hereinafter be more fully explained.

Slidably'mounted upon the outer sliding,

section Of tllfi bar is a sleeve 17 which carries a mirror frame 18 and similarly supy ported upon the inner or stationary member of the bar is a second sleeve 19 which carries a test type holder 20.

The 'mirror-frame has two uprights at opposite ends of across piece which by means of a latch 21 is removably fastened upon the slide 17 in transverse relation to the bar. r 1

Sleeves 22 which are slidably'fitted'upon the uprights are provided with bearings for the support of the ends or a shaft 23 which is'fastened along the upper edge of an oblong m' ror v V p The sleeves 22 are secured in their adj'usted positions-on the uprights by setscrews 25, and spring clicks 26 at the ends of the mirror cooperate with notched egments 27 on the sleeves 22 to hold' the mir ror at any one of a determinate number of angles relative to the vertical plane of its axis of rotation.

Slidably androtatably mounted upon the shaft 23 arethe cooperative members 28 al d 29 of an appliance which inithe' operation serves to find points at the upper edge of the-'mirror in the lines ofvision of the eyes of a patient looking into the mirror at the iinagefot a distant object as in the static test, or focusing at the irnagerola "nearer object'as in the dynamic test.

1 Thepoints thus-established. enable the "ar o I The two members ance carry at their outer ends targets 30 V which 'inay be placed across the upper edge 7 of the mirror so as to be visible to a paoculist to look through the retinoscope across the upper edge of the mirror into .thejtovea centralis o1"' the eyes along lines substantially coincident-with their visual of the finding zipplithe line or" vision of the eye while it is looking at infinity to produce the c0ndition of rest required mthe stat-1c test.

Elie mirror-frame 18 isfurthermore pro 'videdwith'a slotted stop 35 in the center of its cross-piece, to secure a flexible tape 36 by which the distance from the eye ofthe patient to that of the operatorand to a test-object upon which it is' focused; are

measured as explalned.

Thetest-chart holder20 which is"moun*- ed upon the slide consists oi'an upright oblong box of preferably rectangular section which is removably fitted inside a correspondingly shaped rim on'ajbase 38 which is fixed upon the slide '19.

- The wall of the box opposite the mirror has an opening to expose a test-chart'39 fastened -'upon the inner surface ofits opposite wall, and a cover 40 fitted'upon the sides of the casing is adapted to close the lower portion of the opening in order to ldaddoxrod test, and are covered when not in use by a pivoted lid 421 A block 43 of insulating material adjoin-s ingfthe flanged bottom piece upon} which the box 20 is fastened vencloses'a small'i'n-v candescent lamp-socket 4st the terminals of which are connected'ln a circuit with an electric cell or other suitable sourceoff elec-v tricity through they instrumentality of two bmdmg screws 45 and 46.

will hereinafter be more fu'lly expose the'upper part of the test-chart only. I

' An incandescent lamp 47 inserted in the socket extends into the box 20 throughan opening in the adjacent side thereofand is positioned adjacent the pointof inter section of the two slots ll in the cover e0, one of which extends in a vertical plane, and the other at right cngl'es thereto.

A number of veryziine wires 48 crossing eachother at the point at which the slots'intersect, form a series of small rectangles which inthe peration of the instrument are counted by the patient to promote a desire forfocusing upon the intersection' of the streaks oi light appearing through the slots the eyes of the patient.

direction. 7 r

The reel and the clamp are 'mounted reing-reel .49 for the measuring tape 36, and a clamp adapted to secure an unwound portion of the tape against movement in either spectively upon sleeves 51 and 52 slidably' fitted upon the extensions otthe base'lior the purpose of varyingthe distance between:

V p f in which theinstrumenti is installed; A roller 53 on the clamp-slide guides the them.

measuring tape unwound from the reel'to cause it to move partially in a; direction transverse: to the supporting bar. 15 by 1ts movement in. a direction substantially par.- allel thereto. H

-A metal plate 54 extending. front the. clamp slide rearwardo'i' the test-typeholder provides aback for theportion of the tape extending between the" reel and the roller, and a pointer 55 on saidpla'te cooperates with two graduatedjscales on the tape to designate certain distances from the eye o-fa patient, required in determining the refractive errors.

The plate 54: also serves as a shield to. pro-V as to lookthrough lenses-thereon into the mirror along lines at opposite sides of the test-type holder. 1

.The stop '8' which limits the rotary movement of the trial-frame bracketon the carrier 5, andthe stop 16 which restricts the movement of the bar 15 upon the end of the U-shaped bracket 12,-cooperate to secure the 7 correct position of-the diflerent parts'of the instrument with relation-to each other and The movement of the carrier in its slideway permits or adjusting the distance'between the patient and the trial-frame in a straight line and the sliding movements of the mirror and the test-type holder on the bar 15'enable the operator toadjust their relative positions in accordance with varying" conditions; p

When making the static or distance test in which'it isreduired that the eye to been amined is broughtto a condition of rest by looking at a distant object such as the testchart 57 shown in Figure 12, the patient broken line 59, pl us the distance between the the object and-the eye maybe readily made of the mirror.

'tances at which the object must appear to the surface in-close pr does not look-atthe object itself but at an image thereof appearing in the .mirrormfl.

The objectisplaced in different positions with relationlto the instrument according to the available space-in the room in'whi chthe tests are made; the position ofgarticles'of furniture in the. room, and other conditions. I The t'est object may-be placed-inanydesired position inwhich it is reflected in the adjustable mirror of the instrument either directly or through the; intervent on 1 Tn 'Figure 10 of the drawings the-1tcst chart. 5? is fastened agalnstanoverhead surface, as for 'example'the ceiling. ofthe room The distance between'the eye 60 or"'the pa ofone :ormore stationary mirrors 58. r I

tient and the mirror, indicated by the mirror and the test chart designated by the distance at whichijthe eyes. of the patient looking at adistant object are' brought to their required condition of rest: 1 i 7 Assuming that the heightiof-athe.room is sufiicient- Ito give the required distance between the test object onits ceiling and the mirror of the instrument, any variations in the totallength of the line of vision between I by the a'djustment ofv the mirror on the bar 15 which atthe same time-,is shortened or lengthenedby movement of its telescoping parts in order to eliminate any' re arward projection which may-prevent the operator from placing the eye close to theupper edge In this connection it should be noted 'that inasmuch as there are certain known diseye ofthc patient in boththe static and dynamic tests, the relativelyslidingparts ol the insjtrumentmay be provided w-ithcoop- -erat1ve devlcessuch as the cl cks 62 and 'notches63 shown'in Figure-1 of the draw-.

therein is changed until line a of vision The operator bein'gjthus enabled to look across the edge of the mirror into the 'to'vea centralis otfjthe eye'along a line which is nearly coincident with the l'ineoivisioii,

now determines the position" or" rhepenaj of intersection 'of'theline ofid'sii-onwvi'tli' I the reflective surface by'placing 'the target of the respective 1 sliding member er the and forth until thetarge't covers theirnage.

of the object in the-sight of the patient looking through the trial-frame.

. After: the target has been placed in this position it is removed from the face 01" the mirror andthe corresponding sight on the adjusted member of the finder indicates the point at which the operator must pass the light" beam of the retinoscope'to look'along thevisual axis of the eye.

ing along a line substantially coincident with the visual axis of the eye'of the patient is enabled to make .a correct .measurement of its refractive errors and that in this respect thepresent invention ishighly advantageous over instruments "of t class in whichthe'operato r is "compelled to look 'alonga line at anangle t0 ,the visual 'flXlS of the eye and at a point in the retina away from the fovea' central1s,'by' reason of Q "the necessity oflthe patient lookin at the andthe sights 34: on the two members give distanttest object in alinepassing either over or alongside the'headiot the operator.

WVhen the (points of intersection of the lines of'vi sion of'botheyes of the patient with thereflective surface have thus been 7 determined, the po nter on one member of the finding {LPPllflIlCBlIICllCZltGS upon the scale of the other member the correct distance between'the' pupils of the eyes required in measuring the refractive errors the points at which the visual axes of the eyes will intersectthe reflective surface when the patient looks at the reflection of a nearer object in the dynamic test.

.The position of the sights 3% relative to the other sights'33 on the members of the finder are ascertained by calculation and inasmuchas W1tl1' very few exceptions, the

, static test precedes I the dynamic test, but

'oneadjustment of the finder is'required to find all the points at the edge of the-mirror along which the operator must pass the retinoscopic light b'eam to look along the lines of vision of the eyes, under examine:

tion in either test.

as In case the height of theiroom, or other conditions, render the, use of an overhead test chart objectionable, the objectm'ay be placed either back of the patient as shown in Figure 9, or backot' the operator as shown Figure 8. i

In each case the image of the object is produced in'the mirror of the-instrument through the intervention of a stationary m rror 58 which is placed sufiiciently high o to permit of the passage of rays of re flected light over the heads of'the patient and theoperator or over thoseot' other persons who while the testis being made, 'pass between the Ob eCt and [the patient.

During both thestatic and dynamic tests the: end of the tape may if necessary be It will be readily understood by lthose versed in the art that the operator by look-V 116 same,

attached to the mirror frame,yas shown in Figure 7 to measure through the-inter-' mediary of the pointer the distancebetween the operator and the eye or the distance at which the eye sees test-chart.

7 To obtain .botl these measurements, the

tapehas in addition to the scale which indi-V cates the distance' between the mirror and the eye of 'ai'patient seat-ed behind the test frame, another scale which givesthe d1sthe reflectedimage of the tances at which the eye sees itheimage of the object. V

The last-mentioned by'adding to the distance between. the eye and the mirror along the line of vision, the

distances are found distancebetween'the mirror and the object 7 f along the'line of reflected light-underthe conditions illustrated in Figure lO, orhthe sum of the distance. between the auxiliary;

mirror and the mirror 24 of the instrument, and the distance between theauriiliary e ,IIHII'OJ; and the ob ect, as in thewconstruc-fl tion shown in Figures 8 and 9. v

While the. static test is" being made, the

may be removed and a cap 64: placedover the incandescent lamp to direct thelightfocusing powerof the eye under examination it is essentialthat these types are successively brought. intheline of vision at the pointer, as shown distances from the eye corresponding with the aforesaid predetermineddistances,

1th this obj ect n view; the mirror Qtis .utes) at: predetermined distances fromthe eye and 1n order to correctly asicertainthe moved along the'bar l5 topoints at different distances from the test chart mills-holder; which are readily ascertained ,by the '00- 1 operativeclicks and notches on the relatively sliding parts, hereinbeforereferredto.

' After the mirror at the farthest 'dis- Ltancegfrom .the'chart, has been adjusted'to ring theilowermost test-type inthe line of VlSlOn, of the patient as-shown diagram znatically in'Figure 11 of the dmiwings, it '1' s moved. toward the test-type holder until the-next succedingtest-type isv in thelin'e. of 7 ision and this movement is continued unf til the approximate eye is ascertained. 7

focusing power of th'e .96 testtype holder used in the dynamic test h the visual axis, the directions" of which are 1 Withthe mirror and the test chart thus relatively positioned, the oculist examines the eyes by looking through the retinoscope across the upper edgerof the mirror and along hnesapproXi-mately coincident with found by the position of {the sights on the finding :appliance which was adjusted during'the preceding}sta-tic'test f at-which-the patient sees the image ofjthe test chart upon which the eye is focused, by l the registratlon of' ts-scales; with the stationary pointeiyand it maybe held in place after the desired ineasurenientsare ohtalned,

7 by meansof the clamp 50.

Afterithe measurements have been not ed by :the position of thegr'aduations' on -the two scales of the measuring tapewith relat-IOHY EO the stationary. pointer, the opera tor fastensthje hook at the end'of the tape I oftest types positioned-in the box to be re-:

in an eye of-the'retinoscopean'd by looking through the rctinoscope at the eye of the patient, moves the same-away from the lnir-f ror'in one direction or theother in order to determine the reversal'or true focusing point of the eye.

Should this point of reversal be found to bebeyond the distance measured on the- Scale; t e yeflof the patient is lacking in focusor accommodation and 'if'the true focusisfound to be less than the previously measurea distance the eye is over-acconinit')dating.

Theamount of 121 or over-accommodation is calculated by deducting from or adding to the-distancemeasured 'on the scale of the' tape, the distance between the eye and the true focusing point found by the moveme'nt of"the'retinoscope to whichthe tape is attached as h ereinbefor e explained.-

I f'in the dynamicexamination it is necessary tofocus theieye continuously upon afixed object during a prolonged period, the cover 40 is placed-upon the box'wi-th its side covering the intersecting slots 'so that is--yisible. i 3 i c To testgthe muscle strength -of-the eye the lid is turned to cover the upper portion of-thecoyering in the box and uncover'the intersecting slots upon which the pat ent i focuses the eye under examination by counting the squares} between the crosslng wires 48 as h'ereinbefore explained. s

It will be *understoodthat the width of the test-type chart and'th'e holder *in whichit is mounted must be restricted so as not to obstruct the'lines of vision between the veyes of a patient-looking"throughthe lenses in the trial frame and the mirror inwhichthe image of'the'test-ohpct appears;

only the uppermost test type on the chart i-laying thus ,described my improved frefiector inqthelb est forin atpreSe11t knoWnto "me, it :will be understood that variations 111 details of construction and arrangementsof parts maybe resorted towithin the spirit of the inventionas defined in the following;

' 1, In an instrument of the cha1"EL-C f d 1 in therhox, alitest type'lin the box, anda re- 'scribed,l-theconibin'ationiof a, mirror, hlb ox having an opening facing the same, a'lainp movable cover for theopening. of 5 the: box,

havinga: slot forthe emission of light rays.

others. v 3. 111. anginst-rumentof the character idef-i Y to partially close the openingr for the mate,

tron ofoneof the test types exclusive of the F- scrib ec, the combination of ainirrona bOX having ail-opening facing the s'an1e',.a, series 'flected inthe mirror, axcover 'adapted'tofpar- 'tially closethe. opeinng .for the reflectionof one of 'thefteshtypesexclusive of {the-othersand having a slot for the emission of light rays," a lamp in the box, 'ancl an' adjustable. lid or the cover' adapted-to either cover said slot enclose the uncovered-i'portion o'f' v vtheopening.v 1 H ve-jlin'an instrument of the character described, the combination of a fsupporh-a' test-ohjcct-,'a mirror to reflect-the objectin the line of Vision ofaperson occupying a cdeterm'inate' position with relation j to thesupport, 'a' winding measuring tape'l on the support, movable to measure the'dlstanceat which thern'irror 1s POSItIOIIQClfIOHl'. a-person occupyingfsaid position, "and the distance at which the operator is poslti'on'ed "w th: rela-o tion" to" the tion.

mirror, in :re-tinoscopic exaininw In lIldIlSti'lUfiGIlf of the chara'cter described, the'combination of a support, a} test 7 object, mirror to refiect the object in the; line of sion ofa person-occupying a deterininate position with relation to the support, a'-\vincling measuring-tape on the support, movableto measure the distance at which the mirror is positioned' from' a person" occu pying' said position',-'ancl "the distance at? which the operator is positioned with relation to the nm *or," inretinoscoplc exam na; tion, anda'c'la np on the support to secure the tape in its adjustedpositio'n.

port to vary its distance from axpersonoccupying SitlCl POSlfilOIlffi; Winding measuring tape on the support,.movable to measure the distancefatrw iich the mirror is positioned from a person occupying said position, and

the distance ativhich the operator is positioned With relation tothe mirror, in retinoscop c examination, the mirror. and the tape having cooperative means for their connec- L .1 V t1on. j;

7. in,an.instrument-ofthe character described,;the combination of a .support,-.a

horizontally extending, longitudinally contractible. bar there'ointest ob ects, and ap1voted' mirror slidably mounted on the bar 7 with relationto the testobjects and adapted,

toreflect the objects inthe line of vision of person occupying a determinate position with relation to the support.

. 8. in-an instrument of the character described,.the combination of a support, a horizontally extending bar thereon, a testtype, a. mirror mounted .on the bar to reflect.

the test -type in theline of Vision of a person occupying a determinate position with. rela-. ti'onto 'the support, a ivlndingineasur ng tape,,coop'erat1vemeansjcausing t to move partially in a direction transverse of the bar, by its movement in a direction'substantlally parallel thereto, and a pointer cooperat ng with the transverse portion of the tape.

9fIn an instrument of the character described, the combination of a support, ahor1 zontally extendlng bar pivoted thereon,v a

stop determining the operative position ofv the bar relative to the support, a teSt-Ob ect,

and a mirror on the bar for the reflection of the objectintheline of vision of a person occupying a determinate position With rela-' tion to the support.

10. In an instrument of the character described, the combination ofa carrier, a sup- I port pivoted there.on,-a stop determining the operative position ofthe support with relation to the carrier, a trial frame on the sup-f port,zatest-object, and a mirror mounted to rcflect'the objectin the line of vision of a;

person looking through the trial-frame.

11. In an instrument of the character described, the combination of acarrier, a sup port pivotedthereon, a horizontally-extending bar pivoted on'the support, stops determining the operative positions of the sup. port and the bar relative to the carrier, a

test-object, and a mirror on the barto reflect the object in the line of vision of a person occupying a' determinate position With relation to the support. 7

,12. In an instrument of the character described, the combination of a slidable carrier, a support pivoted thereon, a trial frame on the support, a horizontally extending bar pivoted on the support, stops determining the operative positions of'the support and tween said points.

bracket. 2 I 18. In an instrument of the character dc the bar relative to the carrier, a test object,

and a mirror on the bar to .reflecttheobject-E in the line of visionof a person looking through the trial frame." V 3 13. In an instrument of the character described,the combination-of a support, a testobject, a'mirror mounted toreflect the object in the line of visionof a person occupying a determinate position ;Wit hrelation to the support, and a finder having-a slidin'ginoveiment back of the 'mirror along the ,upper' edge, thereof, and including, a sightwvhich determines a pointed; which the observer looks along the line of visionof 'apatient focusing in the mirror, .andan-opaque target alined with the sight and adjustablefto cover a part of the mirror below. the same- 14. In an instrument of the character do? scribed, the combination of a'support, ai

test-object, a. mirror mounted. to reflect the 7 object 1n the line of v1s1on.of a-personoccue pying a determinate position with relation;

to thesupport, andfa -iindcr comprisinga pair of members having a sliding movement- Y back of themirror along the upper-edge thereof, said members having sights which determine poi nts at which the observer looks in-the lines of vision of a person focusing inthe mirror, and cooperative:scale-parts on the members to measure the distance be- 15. In an instrument of the character de scribed, in combination, a;horizontally'sliding carrier, abracketdepending from thej jecting arm, a stop located inthe path] of.

said arm and limiting the movement of the bracket, a trial frame on'thebracket, and a test object. connected to the bracket opposite to the trial frame.

17. In an instrument-of the characterde scribed, a slidevvay 'ada-ptedto'be fastened to an upright support, a carrier movab-lein carrier and having a projecting arm, andia trial frame onthe, pr ecting arm of'the scribed a slideWay adapted to be fastened to an upright support, acarrier movable inv said slideWay, a bracket depending from and movable on the carrier jand having-a project ng arm, a stop located inthejpath of the arm limiting" the movement of the time a I 10o i and a test object connected-t0 thebracket H bracket, and a trial frame onthe projecting arm of the bracket.

19. InIan instrument of'the character de} 7 said slideway, a bracket depending from the 1 scribed, in combination, a test object, a mirror facing the same, and a sliding finder on the mirror, having at the upper edge there- 7 of, a sight to establish'a point in the line of vision of a person'looking at an image of the test objectin' the mirroiy in the static test, and a second slght at a determinate distance from the other, which simultaneously establishes a point in the line of vision in the dynamic test.

20; In an instrument of the scribed, in combination, a test object, a mirror facing the same, and a sliding finger on themirroiyhaving at the upper edge there.

beyond the line of visual axis of the patient and having dissimilar test types arranged in vertical succession, "a slanting mirror facing the chart, and means for compelling a patient to focus at an image in the mirror along a determinate line of vision, the mirror being movable in a straight line relative to the chart whereby tobring its types succharacter de-' c essively in-the line of, vision of the patient.

2-2f1n an instrument of the character described,.the co-mbinationof an overheadtest object, a slanting mirror located beneath the test object to reflect the same, and movj able toward and from the patient, there lie-J ing sufiicient space immediately back and above the mirror to permitan-observer to V loolcacrossthe upper edge of thewm'ir'r'or into. the eye of the patient alongthe'line; of,

visual axis, and a measuring tape'connected for measuring the distance therpatienth 23. In an instrument of the character'described, the combination ofa chart havin dissimllar test types arranged in vertical succession, a slanting mirror facing the chart, and means for compelling a patient 7 to focus at an image in the mirror alon'g'a determinate line or vision," said chart being located outside of the line of axial vision of the patient, and the mirror being movable in a straight line relative to the chart Whereby to bring its; types at different elevations successively in the line of Vision of the patient.

to and movable with the mirror in the 'back- 7 Ward and forward movement of theq'samefrom the eye of In testimony whereof I have afiixed my signature.

I CHAR-LES a. ARMBRUSTER. 

